Adjusting firing rate

Al Letellier

Any domestic water on this system? The only way to adjust input is with orifice size and then time the meter to make sure of input. Your load is quite light for this boiler, but I wouldn't fire it any less that 65% of rated load. Be careful of your combustion readings and adjust properly

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Lamont Hayes

Adjusting firing rate

How doI fire a boiler to the connected radiation? I am serviceing a Utica stm. boiler with an input of 112,000 BTU of natural gas, with the connected radiation of 150 EDR. How do I adjust and determine the proper firing rate?

Unknown

Is the boiler firng

at rated input? If it is then you can not increase past the recommended input. If you do then a combustion problem will be encountered and you will be eventually making carbon monoxide.

To determine if input is correct you can use the test dial on the meter and with the boiler running let the 1/2 foot dial go around twice and clock the seconds it takes for two rotations. Then divide # of seconds into 3600 (number of seconds in an hour) this will give you Cubic Feet Per Hour. You will then need to know the BTU content of gas in your area (usually around 1025 to 1050 BTU's per cubic foot). Multiply BTU content times CFH and this will give you BTU's per hour.

Example:

1/2 foot dial two rotations in 20 seconds

3600 divided by 20 = 180 CFH

180 CFH x 1000 (BTU content) = 180,000 BTU's

Glen

Does your calculation hold true for all sizes of test dial? I ran a few hypothetical calcs - and as long as two revolutions with the half cuft dial were used it seems to hold true. Otherwise I use 3600 divided by seconds for ONE revolution X size of test dial X calorific value of fuel. If more than one revolution is used then the size of the test dial must be multiplied by the same number of revolutions. That said - offering advice on adjusting firing rates without knowing all parameters is questionable ( no Tim - that is not a jab at you - just covering previousy discussed items in one post :-) ). What about elevation and other considerations???? Perhaps the listed maximum manifold pressure is already achieved and still may be under fired according to the rating plate. Or what if it is severely over fired (confirmed by clocking) but still within maximum manifold pressures on the rating plate? Depending on combustion analysis and published manufacturer's specs we can over fire a slight amount in this area (10%) BUT this is only done with the Gas Inspector fully aware and in agreement with the equipment set up. Most times - it is the manufacturers specs that form a higher "code" that our CSA B 149.1

Unknown

Glen, your

formulas are correct, good post I hope the gent who posted has not left us.